As is known, some models of automotive front or rear lights are so small that the conventional bayonet-type filament light bulbs cannot be used as light sources.
In such cases, the manufacturers of automotive lights are obliged to use special filament light bulbs consisting of a glass bulb which ends in a substantially wedge-shaped head or plug which is structured to be inserted/pressed into a specific coupling seat realized in the socket, and which houses the ends of the rheophores that allow the electric current to be carried to the filament housed inside the glass bulb.
These special incandescent light bulbs are traditionally called wedge-base light bulbs, because the terminal head or plug is usually made in one piece with the glass bulb that houses the filament, and they clearly require special sockets that are specifically structured so to hold the wedge-shaped head or plug of the light bulb in place in rigidly and firmly, though easily removable manner, ensuring at the same time the electric current supply to the filament of the light bulb.
In particular, the wedge-base bulb sockets that are mounted in front or rear automotive lights generally consist of a plastic-material supporting plate or base which is generally incorporated into the rear body of the automotive light, and is provided with a coupling seat shaped to house the terminal head or plug of the wedge-base light bulb; and of two tongue clamp connectors which are housed on the bottom of the coupling seat, and are structured so as to embrace and grip two separate portions of the head or plug of the wedge-base light bulb, in order to hold the head or plug of the light bulb firmly in the coupling seat.
More specifically, the two tongue clamp connectors are made of metal, and are structured so as to permanently touch the two rheophores which emerge from the terminal head of the wedge-base light bulb; and the socket is also provided with two metal straps, i.e. made of an electrically conductive material, which are structured so to electrically connect the two tongue clamp connectors to the motor-vehicle electric circuit, or rather to the electric circuit arranged on the body of the automotive light and which, in turn, is connected to the motor-vehicle electric circuit.
In some socket models, the two electric feeding straps are even structured so as to connect the two tongue clamp connectors to the electric circuit on the rear body of the front or rear automotive light, and at the same time so as to hold the two tongue clamp connectors on the bottom of the coupling seat realized in the supporting base.
Unfortunately the tongue clamp connectors that hold the terminal head of the wedge-base light bulb in place in the coupling seat are extremely sensitive to mechanical vibrations, with all drawbacks concerned when the sockets of the type referred above are used in an automotive light.
When used in this application context, in fact, the vibrations and jolting occurring during the normal use of the vehicle can cause the wedge-base light bulb to become misaligned with respect to the optical axis of the light reflector, with the subsequent deterioration of the quality of the light beam emitted by the automotive light, or even cause the light bulb to come right out of the coupling seat, making the automotive light completely useless.
Some automotive lights manufacturers have at least partially overcome this problem by providing the wedge-base bulb sockets with an additional centering sleeve structured so as to be removably fitted/connected to the entrance of the coupling seat realized in the supporting base. This removable sleeve is also structured to grip the neck that joins the glass bulb to the plug, so to hold the wedge-base light bulb always in the right position inside the coupling seat, i.e. perfectly coaxial with the optical axis of the reflector which is suited to project/direct outwards the light of the light bulb.
More specifically, with reference to European patent No. 1633024, the additional centering sleeve is provided with a number of projecting centering tongues which sticks out from the upper perimetrical rim of the sleeve, and which are suited to abut against the neck of the glass bulb when the wedge-base light bulb is correctly inserted in the socket, inside the centering sleeve.
Unfortunately, since it has to remain in direct contact with the glass bulb that normally reaches temperatures of much more than 100° C., the removable centering sleeve must be made of a plastic material having extremely good heat resistance properties and which is, thus, more valuable and expensive than the material generally used to make the supporting base of the socket, with the resulting significant increase in the production and assembly costs.
Moreover, the socket with additional centering sleeve cannot house wedge-base light bulbs of different sizes, because the additional centering sleeve is structured to surround and support only one specific model of wedge-base light bulb.